The present invention relates to a method, apparatus and program for alarming abnormality in tire air-pressure.
Conventionally, a method for alarming abnormality in tire air-pressure that detects decrease in tire air-pressure and generates alarm detects whether tire air-pressure is decreased or not by the variation of judgment value (DEL) calculated, for example by the equation (1) from the rotational speeds of respective tires utilizing that the rotational speed of a decreased tire is faster in comparison with the rotational speeds of tires with normal air-pressure and generate alarm when decrease in tire air-pressure is detected. Further, in the equation (1), FL shows the speed of a front left wheel, FR shows the speed of a front right wheel, RL shows the speed of a rear left wheel and RR shows the speed of a rear right wheel.DEL=((FL+RR)/(FR+RL)−1)×100  (1)
In the method, there are known methods such as, for example, a method of providing difference between threshold for judging the deflation of driven wheels and threshold for judging the deflation of drive wheels (refer to Japanese Unexamined Patent Publication No. 2003-54230).
However, when air suspensions are actuated in a vehicle equipped with air suspensions and the heights of strokes are different in left and right sides, loads applied on respective left and right tires are changed. Further, the dynamic load radius of a tire differs depending on load applied on the tire, and the larger the load applied on a tire is, the faster the rotational speed is.
Accordingly, for example, when the air suspensions are actuated, it cannot be judged whether it is caused by decrease in tire air-pressure or by the actuation of an air suspension when the rotational speed of a tire of one wheel increases, therefore there has been a problem that it causes erroneous report and no alarm.